Stability Study of Herringbone-grooved, Journal Gas Bearing for Small Cryogenic Expansion Turbine

Abstract

This chapter presents the theoretical and experimental studies for the stability of herringbone-grooved, journal gas bearing (HGJGB) for small cryogenic expansion turbine (SCET). The dynamic characteristic of HGJGB has been obtained by finite element method (FEM) and the difference of two cross stiffness coefficients is used to evaluate the stability. A SCET has been designed and on which some HGJGBs with different parameters have been tested. The experimental values are in good agreement with the numerical results. The method of evaluating stability by comparing the difference of two cross stiffness coefficients has been proved to be effective. Some conclusions which are useful for designing small HGJGB expansion turbines under the experimental conditions are––“the instable speed increases with A and the increasing speed decreases,” “when A is larger, the optimum groove depth approximately equal to the radius clearance of ridge parts,” “the instable speed increases with groove angle, and the instable speed increases with the ratio of groove width.”